Mixed conductors having both high ionic and electronic conductivities are needed in membrane electrode assemblies (MEAs) present in electrochemical devices from fuel cells to supercapacitors and all battery chemistries. Typically, carbon black, binders, and redox-active materials are combined to make an electrode assembly, into which a liquid electrolyte can impregnate. Solid-state devices require the ionic conduction built into the MEA. In this case, a material which can provide both electronic and ionic conduction as well as a redox functionality is described based on PEDOT−Cl as both the electronic conductor and the redox active component, while an organic ionic plastic crystal [C 2 mpyr][FSI] is present as both the binder and ionic conductor. Surprisingly, both the electronic and ionic conductivities of the composite are enhanced relative to the pure components by a factor of ×9 for electronic and ×180 for ionic conductivities. The mixed conducting composites are demonstrated to retain their redox activity in aqueous electrolytes, and in the optimum case, 103 F g −1 and 296 mF cm −2 capacitance values are obtained for low-and high-mass loading electrodes. These materials demonstrate an innovative approach to prepare electrode assemblies where all three functionalities are incorporated into the materials, that is, electronic, ionic, and redox activity for future energy devices.

This article presents PEDOT:PSS/cholinium IL composites to design safe bioelectrodes for long-term cutaneous recording. The PEDOT:PSS/IL composites presented improved electronic and ionic conductivities, as well as injectable properties.